The present invention is directed to an arrangement of two optical waveguides which are integrated on the surface of a substrate for the respective guidance of an optical wave along a respective axis.
In integrated-optical circuits, various demands are made of the employed waveguides, dependent on their functions: passive elements like filters or switches are usually based on structures of coupled waveguides that require a weak wave guidance for achieving a compact dimension. A strong wave guidance is needed for curved, connecting waveguides in order to obtain a tight curvature radius due to the occurring emission.
It is possible to employ one waveguide type for all sub-components, whereby the wave guidance is set so that all demands are met to a satisfactory extent. The structures designed according to this compromise are long and narrow. The structural length of the chip is relatively great.
European Application 0 285 351 discloses an arrangement of an optical waveguide integrated on the surface of a substrate that proceeds straight in sections and is curved in other sections. The radiation losses of the waveguide are reduced by trenches arranged at the outside of a curved waveguide.
The article by Koai et al entitled "Modeling of Ti:LiNbO.sub.3 Waveguide Devices: Part II--S-Shaped Channel Waveguide Bends" from the Journal of Lightwave Technology, Vol. 7, No. 7, July 1989, pp. 1016-1022 discloses how the course of a curve in a curved waveguide can be optimized with respect to radiation losses.